I wonder if there is a list of features implemented in JBoss AS 7, but missing from the WildFly 8? It would make migration assessments way easier.
Maybe JASPIC is still open. All the tests in the Java EE 7 samples project are still failing. This may be an issue with the tests themselves, with the way JASPIC needs to be setup in JBoss products (ideally no setup should be needed, but alas), missing functionality or any combination of the above.
At any length, I can't yet run any application that depends on JASPIC on WildFly, so this obviously makes migration of these apps impossible.